Pneumatic tank trailers (also referred to as “dry bulk trailers”) are semi tractor trailers having pressurized tanks for carrying dry cargo such as concrete, dog food, corn, grains, flour, and sand, to name a few. The dry cargo is loaded into the tank at its top through cargo hatches and unloaded through a bottom discharge under pneumatic pressure. Each hatch includes a peripheral lip defining a hatch opening, a hatch cover that pivots between a closed position covering the hatch opening and an open position uncovering the hatch opening, and multiple levers (also referred to as “dogs”) pivotally repositionable between a locked position securing the closed hatch cover and an unlocked position permitting the hatch cover to be moved to the open position. The tank hatches must be manually opened (typically by the driver) to load the cargo, then after loading the tank hatches must be manually closed.
Operating the hatches by hand is quite difficult at best, opening them much more so than closing them. That's because the tank must be pressurized to “blow off” the cargo it's carrying under considerable pressure (typically about 7 psi to about 12 psi), and in order to maintain an airtight seal at the hatches under these high pressures, the hatch-securing mechanism must be quite substantial in its construction. Typically there are six (sometimes more or less) of the pivotal levers that tighten-down each closed hatch cover by cam action to form the airtight seal under high pressures. And the hatches are on top of the tank, typically at or above twelve feet off the ground. So the operator must climb a ladder on the trailer to get to the top of the tank, bend over at the waist, jerk with considerable force on the handle of one of the levers—exerting an incredible amount of pressure on the lower back—to unlock it, repeat the unlocking step for all the other levers for that hatch, open that hatch, then repeat as needed for multiple hatches. Many drivers of pneumatic tank trailers have been known to say that the act of opening these hatches is the most difficult part of their job. In fact, the act of opening these hatches by hand has led to many on-the-job work-related injuries. And although an automatic powered hatch has been developed for ease of operation, they are extremely expensive and thus not commonplace.
Accordingly, it can be seen that needs exist for improvements to enable hatches of pneumatic tank trailers to be operated more easily. It is to the provision of solutions to these and other problems that the present invention is primarily directed.